JPH05154889A - Stopping method for molding machine - Google Patents

Abstract

PURPOSE:To obtain a molding machine stop method by which at the restart of molding after the stop of a thermoplastic resin melt molding machine, generation of foreign matter is inhibited, a steady state for the molding of non- defectives can be accomplished in a short time, and a replacing timing of a device can be extended. CONSTITUTION:When a molding machine used for melt-molding a thermoplastic resin is brought to a stop, a screw is extracted while the resin in the molding machine is in a molten condition, and the molding machine is stopped with the resin adhering over the full inner wall surface of a cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stopping a molding machine used for melt molding a thermoplastic resin. For more details,
The present invention relates to a method for stopping a molding machine that can reach a steady state in which a non-defective product can be obtained in a short time when the molding is restarted and can extend a cylinder renewal time.

[0002]

2. Description of the Related Art A thermoplastic resin melt molding machine may be stopped for a long period of 10 to 30 days or more for periodic inspection or repair. In this case, conventionally, due to the work procedure and setup, the screw is pulled out at the same time as stopping the device, and the resin on the inner wall surface of the cylinder is immediately removed and cleaned.

However, even after careful cleaning, rust occurs on the entire inner wall surface of the cylinder within 2 to 3 days. Even if you carefully remove rust and start again when starting molding,
Foreign matter continues to be mixed into the molded product, and it is necessary to purge a large amount of resin. In addition, the product remains unstable for a long time before it becomes a good product, resulting in a great loss of material and time. Further, due to the corrosion of the inner wall surface of the cylinder, the clearance with the screw becomes large, the molding ability is reduced, and the renewal time of the device is unavoidable.

[0004]

SUMMARY OF THE INVENTION According to the present invention, when the molding machine is restarted after the melt molding machine for the thermoplastic resin is stopped, the generation of foreign matter is suppressed and a steady state where a good product is obtained can be reached in a short time. It is an object of the present invention to provide a method of stopping a molding machine, which is capable of extending the time for renewing the apparatus.

As a result of earnest studies on the generation of rust on the inner wall surface of the cylinder, the present inventor found that the resin on the inner wall surface of the cylinder is left as it is without being removed, so that the contact between the wall surface and the atmosphere is interrupted and the rust is generated. The present invention has been completed by demonstrating that such a phenomenon is prevented, the steady state is reached in an extremely short time after resumption, the renewal period of the device is extended, and the economic effect is great.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, when a molding machine used for melt-molding a thermoplastic resin is stopped, a screw is pulled out while the resin in the molding machine is in a molten state, and an inner wall surface of a cylinder is removed. The method for stopping a molding machine is characterized in that the resin is stopped on the entire surface of the molding machine.

The melt molding machine referred to in the present invention is a device for melting and molding a resin, such as an extruder or an injection molding machine. Hereinafter, the case of an aromatic polycarbonate resin will be described using an extruder as an example.

[0008] Polycarbonate resin powder having a viscosity average molecular weight of 25300 was melt extruded at a cylinder temperature of 300 ° C and a screw rotation speed of 60 rpm by an extruder of a cylinder of 120 mmφ nitriding treatment to produce pellets.
The case of restarting the extrusion molding after stopping for 0 days was examined.

At the same time as stopping, the screw was pulled out, and the resin was left on the inner wall surface of the cylinder for 30 days. Immediately before restarting, the cylinder was heated to 300 ° C. and the resin was sufficiently melted. Wind the wire in a mesh form and wind it, and clean the inside of the cylinder 10 times while renewing. There was no resin adhesion on the inner wall surface, gloss was generated on the wall surface, and the vent part was cleaned cleanly. Complete the cleaning by visually observing and immediately mount the cleaned screw and die on the cylinder.
When the temperature reached 00 ° C, the extrusion was restarted at a screw rotation speed of 60 rpm. When 50 kg of the polycarbonate resin had been purged, the generation of foreign substances stopped, and after that, the pellets were switched to non-defective pellets, but they were stable. Since the inner wall surface of the cylinder was covered with the resin and shut off from the air during the stop, the inner wall surface was not rusted and only 50 kg of purge was required.

On the other hand, at the same time as stopping the extruder, the screw was pulled out, 120 mmφ wire brush was immediately wrapped with Coppa Cause, and the inside of the cylinder was cleaned 10 times while renewing. Occurred, and the rust condition deteriorated significantly with the passage of time. Thirty
After a day, the same cleaning was started again, but the generation of foreign substances did not stop even after purging 150 kg of polycarbonate resin, and the unstable state continued. Then, the rusted wall surface was cleaned in the same manner, and when this wall surface was observed carefully, it was found that there were places where the wall surface was concave (hole-shaped).
From this, it is considered that the deteriorated resin or rust that has entered this hole is difficult to be removed, and that the generation of foreign matter continues forever.

The thermoplastic resin to be melt-molded in the present invention is not particularly limited as long as it is a thermoplastic resin to be melt-molded, and such a thermoplastic resin may be separated, for example, according to need. Inorganic or organic additives generally used such as molds, ultraviolet absorbers, stabilizers, colorants, and reinforcing agents may be added. In particular, a thermoplastic resin that does not adversely affect the cylinder or the like of a molding machine is preferable, and an additive to be compounded is preferably one that does not adversely affect the cylinder or the like. When using a thermoplastic resin that tends to adversely affect the cylinder, etc. or a thermoplastic resin containing an additive that tends to adversely affect the cylinder etc., replace the inside of the cylinder with a thermoplastic resin that does not adversely affect the cylinder etc. before molding It is preferable to stop the machine.

[0012]

EXAMPLES The present invention will be further described with reference to examples.
The foreign matter here is a general term for foreign matter insoluble in methylene chloride. To measure the foreign matter, dissolve 100 g of pellets in 5 liters of methylene chloride, suction filter using Toyo Filter Paper No.3 (for quantitative determination), and filter paper. The foreign matters above were visually counted.

[0013]

Example 1 Polycarbonate resin powder having a viscosity average molecular weight of 25300 was extruded with a 120 mmφ extruder at a cylinder temperature of 300 ° C. and a screw rotation speed of 60 rpm.
The book was extruded and cut with a cutter to produce pellets.
Immediately after extruding 400 kg of polycarbonate powder,
The screw was pulled out, the power was turned off, and the cylinder inner surface was left for 30 days with the resin attached. When the wall surface of the cylinder was restarted, no rust was found. Therefore, the cylinder was heated to 300 ° C, and when it was sufficiently melted, the copper brush was wrapped around a wire brush of 120 mmφ, and the inside of the cylinder was cleaned 10 times while updating.
There is no resin adhered to the wall surface, it is glossy, and it is judged visually that the vent part has been cleaned cleanly, and cleaning is completed, immediately mount the cleaned die and screw on the cylinder,
When the temperature reached 300 ° C, the extrusion was restarted at a screw rotation speed of 60 rpm. When 50 kg of polycarbonate was purged, the generation of foreign substances stopped, and when the pellets were switched to non-defective ones, they were stable. Table 1 shows the results of the amount of purge and the amount of foreign matter after the restart.

[0014]

[Comparative Example 1] In Example 1, the screw was taken out at the same time when the extruder was stopped, and immediately the coil brush was wound around a 120 mmφ wire brush, the inside of the cylinder was cleaned 10 times while updating, and the power was turned off and left for 30 days. .. On the second day, rust was generated on the entire inner wall of the cylinder, and became worse as the days went by. When restarted, the cleaning was carried out again in the same manner, the cleaned die and screw were attached to the cylinder, and when the temperature of the cylinder reached 300 ° C, extrusion was restarted at a screw rotation speed of 60 rpm. After purging 150 kg of polycarbonate, the generation of foreign matter did not stop, and after further purging 50 kg, it finally stopped. I switched to non-defective pellets here, but a foreign matter suddenly occurred and the state of instability continued. Table 1 shows the results of the amount of purge and the amount of foreign matter after the restart.

[0015]

[Table 1]

[0016]

EFFECTS OF THE INVENTION According to the present invention, when the melt molding machine used for molding the thermoplastic resin is stopped and then the molding is restarted, the generation of foreign matter is suppressed, and a good product is obtained in a short time in a steady state. Can be reached, less material and time is lost, and the renewal period of the cylinder can be extended, and the productivity improvement effect is exceptional.

Claims (1)

[Claims] 1. A state in which when a molding machine used for melt-molding a thermoplastic resin is stopped, a screw is pulled out while the resin in the molding machine is in a molten state and the resin adheres to the entire inner wall surface of the cylinder. A method for stopping a molding machine, which comprises stopping at.